(Not Applicable)
The present invention relates generally to repair pressure applicators, and more particularly to a repair pressure applicator having an inflatable bladder for applying pressure against a repair patch.
Typically the surface repair process includes filling a damaged surface region with an adhesive or other filler material so as to bring the surface of the damaged area flush with that of the adjacent undamaged surface areas. A repair patch is formed to substantially conform to the contour. The repair patch formed so as to overlap onto the adjacent undamaged surface area to obtain a metal-to metal (or composite-to-composite, as the case may be) bond region adequate to hold the repair patch in place. The repair patch is then adhesively bonded to the damaged area with a curing adhesive. The term adhesive is contemplated to include, but not limited to, epoxy resin, glue, cement and other bonding agents. Commonly, the adhesive requires heat to be applied to properly cure the adhesive or to accelerate the curing process.
In addition, trapped air is commonly encountered in the bondline between the structure and the repair patch. This may take the form of small bubbles and volatiles which produce porosity in the bondline. This process which occurs during curing and/or heating processes is sometimes described as volatile evolution or gas migration. During the curing process, however, these small bubbles may grow to become large bubbles or voids which significantly reduce the quality of the adhesive bond. It is known in the art that the application of uniform pressure to the repair patch during the curing process tends to squeeze out the trapped air in the bondline or otherwise mitigate the growth of the air bubbles into larger ones. Thus, the quality of adhesive bonding depends largely upon the application of substantially uniform pressure over the repair patch during the adhesive curing process.
A conventional method of applying pressure to the repair patch on-aircraft repair involves using a flexible vacuum bag or cover. The vacuum bag is positioned over the repair patch and sealed around the perimeter. A vacuum or negative pressure source is applied to the vacuum bag so as to evacuate the vacuum bag, thereby collapsing the vacuum bag and forcing the vacuum bag against the repair patch. The amount of pressure applied to the repair patch is limited by the amount of vacuum pressure which may be achieved. For example, where there are holes or otherwise porous surfaces within the vacuum bagged area, such holes must be sealed prior to achieving adequate vacuum pressure. In addition, the sealing of the perimeter of the vacuum bag may present problems, especially where significant vacuum pressures are required to achieve a corresponding desired repair patch pressure.
Another method of applying pressure to a repair patch involves using tooling constructed specifically for a given repair. Obviously, such repair specific tooling is costly, labor intensive and inefficient.
Where the adhesive is a heat-curing adhesive, a heat source is additionally applied to the repair patch in conjunction with a pressure applicator. A conventional method for applying heat is through the use of a heating blanket.
Furthermore, surfaces in need of repair, such as those of aircraft, often are not located on smooth, flat, upward-facing areas. As such, repairs typically need to be effectuated surfaces which may be vertical or even downward facing. In addition, where the repair surface is located at an area which is contoured, the repair patch may be oriented significantly different from those surfaces immediately adjacent to the repair patch. For example, the convex curvature at the leading edge of an aircraft wing and the concave curvature where the wings intersect aircraft fuselage present potential repair areas where the aircraft surface at the repair patch is significantly different from adjacent surface areas. Conventional pressure applicator devices may not be readily deployable at such contoured regions.
It is therefore evident that there exists a need in the art for a pressure applicator device for applying pressure to a repair patch during the curing process which facilitates repairs, applies substantially uniform pressure to the repair patch, accommodates the use of a heat source, such as a heating blanket, and is deployable adjacent a variable contoured surface.
In accordance with the present invention, there is provided a pressure applicator device for applying pressure to a repair patch of a surface. The pressure applicator device is provided with a suction member for providing suction attachment to the surface about the repair patch. The pressure applicator device is further provided with a cover member which is disposable above and across the suction member. The cover member is attached to the suction member. The pressure applicator device is further provided with a flexible pressure bladder formed of a generally fluid tight elastic material which is disposed beneath the cover member and interior to the suction member. The pressure bladder defines upper and lower chambers. The upper chamber is disposed between the cover member and the pressure bladder. The lower chamber is disposable between the pressure bladder and the surface. The pressure bladder is sized and configured to apply pressure to the repair patch upon fluid evacuation of the lower chamber. In addition, the pressure bladder may be sized and configured to extend towards the cover member upon fluid evacuation of the upper chamber.
It is contemplated that the fluid conditions within the upper and lower chambers may be selectively controlled. In this regard, in the preferred embodiment of the present invention, the pressure applicator device is further provided with an lower port in fluid communication with the lower chamber for selectively controlling pressure within the lower chamber. The lower port is ventable to ambient fluid conditions external to the pressure applicator device. Further, the lower port is attachable to a vacuum source for fluid evacuation of the lower chamber, and attachable to a pressure source for fluid increasing the fluid pressure within the lower chamber. Similarly, the pressure applicator device is further provided with an upper port in fluid communication with the upper chamber for selectively controlling pressure within the upper chamber. The upper port is ventable to ambient fluid conditions external to the pressure applicator device. Further, the upper port is attachable to a vacuum source for fluid evacuation of the upper chamber, and attachable to a pressure source for fluid increasing the fluid pressure within the upper chamber.
In the preferred embodiment of the present invention, the suction member is generally annular and a generally annular gasket is disposed between the pressure bladder and the suction member. Lower port is integrally formed with the gasket and extends radially inward towards the lower chamber through the gasket.
Further, the suction device may be provided with a generally annular outer seal disposable around the repair patch, and a generally annular inner seal disposable radially interior to the outer seal and around the repair patch. The outer seal and the inner seal are configured to form a vacuum seal within the annular region therebetween. In this regard, the suction device facilitates a significant attachment area for allowing secure attachment of the pressure applicator device. In addition, a heat source may be disposed adjacent the pressure bladder for transferring heat to the repair patch upon application of pressure to the repair patch by the pressure bladder. In this regard, the heat source may take the form of a heat blanket which may be integrated with the pressure bladder.
The present invention overcomes limitations associated with prior art pressure applicator devices. The limitations encountered with the vacuum bag method of applying pressure are mitigated in that the pressure applied to the repair patch is not limited by the vacuum bag seal achieved. In fact, the pressure applicator of the present invention may be deployable on top of a vacuum bag arrangement for applying additional pressure beyond that applied by the vacuum bag. Advantageously, the present invention facilitates the selective application of pressure by the pressure bladder to the repair patch. Further, the environment within the upper and lower chambers are controllable. In this regard, the lower chamber may be subject to a vacuum draw. Such lower chamber vacuum draw may be effectuated without the application of downward pressure on the repair patch, as the upper chamber may be evacuated for maintaining the pressure bladder in an upward position away from the repair patch. It is contemplated that such lower chamber vacuum draw encourages the release of volatiles from the repair patch and facilitates the removal of such volatiles. Subsequently, the vacuum draw within the upper chamber may be removed and vented to atmospheric pressure. In this regard, the pressure bladder is contemplated to apply a positive atmospheric pressure to the repair patch. Should further pressure be desired, the pressure within the upper chamber may be increased and thereby increasing the pressure exerted by the pressure bladder to the repair patch. Further, as mentioned above, the pressure bladder may be utilized with the addition of a heat source. As such, it is contemplated that the present invention facilitates a broad range of curing processes which include the combinations of applications of pressure, temperature and volatile venting previously not available by a single tool or device.